Completely disappeared without a trace. And deserters, who should have been brought back from previous installments of Heroes.

Books, of course, can be found online. It's just that you can make the White Dragon an 8th-level creature. Now, regarding the dragon that occupies 8 squares. It's desirable not for the hero, but as something like a boss. And let it block attacks. In the case where a huge army is attacking a single, ancient dragon, the maximum number of units should be able to approach it to attack, otherwise, it will defeat them all, but here, one unit attacks, the dragon responds accordingly, and the others attack it without provoking a counterattack. This is better. In any case, such a creature is something new. It's not the tiresome army of darkness, which has the same units; it's a monster that the hero will hunt. And there's no need to populate the map with them; otherwise, it will be like in Heroes of Might and Magic III½: In the Wake of Gods, where the map is simply teeming with dwellings of level 8 monsters created on a random map, and the computer-controlled players only buy them.